hi don,
do you think your pump may not be performing up to spec?
my '64 fury street car has a mallory pump located similar to yours with a mechanical pump (i use this pump as a regulator and so i do not get stranded if i have a e-pump failure). i run a holley double pumper with out any problems at high RPM (11.89 et). i would check your pump out before going to a cell and all the associated plumbing (unless you want to).
if you do go to a cell, look at the way i did it on my '65 satellite so you do not end up cutting up your trunk floor.